NCSoft has put online a brief letter to respond to all the fan requests and petitions to avoid the closure of City of Heroes. Apparently, quite a few attempts were made at finding a solution, but in the end they had to settle down with the MMO closure:

We wanted to let you know that your voices have been heard and your concerns have been taken into serious consideration. We appreciate the overwhelmingly constructive and positive messages in the emails, notes, and packages you've sent in support of the game. It has not been an easy decision for us to close Paragon Studios® and prepare to shut down City of Heroes. We've exhausted all options including the selling of the studio and the rights to the City of Heroes intellectual property, but in the end, efforts to do so were not successful. City of Heroes has a special place in all of our hearts, and we want to ensure its reputation and the memories we share for the game end on a high note.